Rectifier roll arrancement



- Jan.V l2, 1965 L.. E. DENNIS ETAL RECHNER ROLL ARRANGEMENT 2 Sheets-Sheet l Filed Dec. 14. 1962 f! 2B 29 L2 2m /24 INVENTORS aa/s f'. Denn/s Byfdwurd 0 eac/r/er TT ORNE YS Jan. l2, 1965 L, E.. DENNIS ETAL 3,165,438

RECTIFIER ROLL ARRANGEMENT med Dec. 14. 1962 z sheets-sheet 2 Y 22o 25, 32201;' 2z] l 2/8 224 v M INVENTORS.

az/As ff Denn/s BYfdIl/fd D. Bearb/9' t@ W @'XRNEYS United States Patent O M 31651433 RECTESKER RLL ARRANGEMENT Louis E. Dennis, Clinton, and Edward D. Beachtet', Beloit, Wis., assignors to Beloit Corporation, Eeioit, Wis., a corporation of Wisconsin Filed Bee. 14, 1962, Ser. No. 244,SZ9 4 tlaims. (Cl. t62-259) This invention relates to headboxes for continuously feeding paper making stock onto a forming wire, and more particularly, to an improved and novel arrangement and structure of rectifier rolls in such headboxes.

Although the instant invention may have use in a number of fields, it is particularly useful in connection with the manufacture of paper in high gallonage headboxes and will be described in detail with respect to this use. In the manufacture of paper, particularly using high gallonage headboxes, the maintenance of the stock in a relatively unflocculated state as it flows through the headbox is a major consideration. The device usually used to achieve this is called a rectifier roll, which presents to the stock stream a rotating perforated cylindrical tube extending lengthwise across the headbox. Usually three or more such rectifier rolls are used in paper machine headboxes, and in conventional practice these may vary from eight inches to twenty-four inches in diameter. In addition to providing agitation for the stock suspension, rectifier rolls serve to even out the velocity profile in the stock stream across the machine. Much time has been spent in evaluating or attempting to evaluate the ability of rectifier rolls to perform these functions in terms of the design variables.

Within such design variables, the rectifier rolls used in the practice of the instant invention comprise a radially perforated cylindrical tube, which usually has a plurality of discs or radial baffles extending across the interior of the tube and axially spaced along the length thereof. The stock fiows transversely of the rotating rolls through the perforations in the tube, and these perforations in cooperation with the radial baffles reduce or minimize substantially cross velocities and eddy currents in the stock streams flowing therethrough, so as to obtain a substantially rectilinear stock flow exiting from the rectifier roll.

It has been proposed to use more than one rectifier roll, for example, in the form of a stack of superimposed rectifier rolls so as to provide reetifying means extending from the bottom of the stock conduit to the top level of the stock flowing therethrough; and it has also been proposed to employ superimposed rectifying rolls to form a bridge of rectifying means immediately ahead of the slice in the headbox so as to obtain a final rectifying of the stock streams just prior to the exit of the stock through the headbox slice, all as more fully disclosed in U.S. Patent No. 2,664,033, issued December 29, 1953, and U.S. Patent No. 2,699,096, issued January l1, 1955. The instant invention provides a novel arrangement for rectifier rolls, and may involve the use of rectifier rolls having essentially the various structural features and functions described in substantial detail in the aforesaid patents. ln addition, the instant invention provides an improved rectifier roll structure particularly useful in the novel rectifier roll arrangement of the invention.

One essential difference between the instant invention and those of the aforesaid patents is that the instant invention relates to a one roll deep7 headbox, which is a headbox in which there are a plurality of (preferably two) rectifier rolls so constructed in the headbox that the stock stream just barely submerges each of these rolls but passes through them successively. The stock stream is thus maintained at a depth of approximately one rectifier roll, the actual depth of the stock stream immediately upstream of any one of such rolls being just barely suflicient lbgid Patented dan. l2, 1965 ICC to submerge such roll (which is operated in close running relation to the floor of the headbox). In spite of the advantages of simplicity which such a headbox affords, operating difiiculties are encountered in high gallonage uses and the instant invention was arrived at only after a rather exhaustive analysis of stock flow characteristics in such a headbox.

The initial difficulties encountered in studying the operation of headboxes of the type here involved were both practical and theoretical in nature. For example, it is well known that rectifier rolls for a given headbox are made to order especially for the particular headbox, in view of the characteristically unique combination of wire width, headbox size, operating speed, etc. conditions and features of any given paper machine. In a given headbox having a number of rectier rolls, an effort is ordinarily made to design rectifier rolls for use at different locations in the headbox so that such rolls will be substantially identical. In such case, the rolls will be interchangeable in the headbox positions and there will be a substantial reduction in the number lof comparatively expensive spare rectifier rolls which a mill must carry.

It is also conventional practice to construct headboxes for many types of paper making machines with generally horizontal floors; and it might at first seem that it would be a simple expedient to construct a one roll deep headbox with a generally horizontal door and provide the same with a pair of substantially identical rectifier rolls, with conventional means for controlling the flow of stock through the headbox, which would include means for controlling the iiow rate of stock into the headbox and/ or means for controlling the gas pressure on top of the stream of stock in the headbox. Such an arrangement, however, has been found to leave much to be desired in certain paper making operations, particularly in high gallonage headboxes. In fact, it will be found that in high gallonage headboxes such an arrangement may result in the formation of paper webs of varying properties giving evidence of undesirable fiow phenomena in the headbox, including a loss of control of the velocity profile, or alternatively, undesirable fiocculation, turbulence and/ or other disturbances in the region of the slice. The instant invention has resulted from not only an analysis of such various undesirable phenomena, but also the development of a solution to the problems analyzed by changes in operating structure and function of the headbox. In addition, the studies of these various phenomena in the headbox have resulted in the discovery of an improved rectifier roll structure for use in the practice of the invention.

It is, therefore, an important object of the instant invention to provide an improved arrangement and structure of rectifier rolls in a headbox.

It is a further object of the instant invention to provide an improved structure and operation for a one roll deep headbox.

Yet another object of the instant inventionis to provide an improved rectifier roll structure.

Other and further objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed disclosure thereof and the drawings attached hereto and made a part hereof. v

On the drawings:

FIGURE l is an essentially diagrammatic elevational view of a headbox embodying the instant invention;

FIGURE 2 is a detail View, with parts broken away and parts shown in section, of the mounting of one end of; a rectifier roll in the headbox of FIGURE 1;

FIGURE 3 is a fragmentary detail view, with parts shown in section and parts broken away, taken substantially along the line III-III of FIGURE 2;

' pheric pressure.

.9 FIGURE 4 is a detail view of the outermost head mounting the stub shaft shown in FIGURE 2, but taken generally along the vertical plane of the roll axis;

FIGURE 5 is an essentially diagrammatic view of a rectifier roll at the tapered approach of a headbox slice;

FIGURE 6 is an essentially diagrammatic elevational view comparable to that of FIGURE 1, but showing a somewhat different embodiment of the instant invention; and

FIGURE 7 is an essentially diagrammatic elevational view comparable to FIGURES l and 6, but showing still another embodiment of the instant invention.

As shown on the drawings:

In FIGURE 1, the embodiment of the instant invention indicated generally by the reference numeral 10 comprises a headbox 11 having a front wall 12, a generally horizontal floor 13, a hack wall 14, and side walls 15 and 16 (FIGURE 2). Paper making stock fiows from a suitable source S, such as a fan pump (not shown) through a control valve 17 and, as indicated diagrammatically, up-

wardly past a conventional throat rectifier roll 18 andl downwardly inclined front wall portion 12a which defines with the floor 13 a tapered approach to the slice opening 22. The downwardly inclined front wall portion 12a is adjustable (by virtue of a conventional pivotal mounting or otherwise), so that conventional adjusting means indicated at may be used to selectively vary the size of the slice opening 22.

The rectifier rolls 1S, 20 and 21 are mounted for rotation and are conventionally driven at selected speeds, for example, by suitable power means such as the motors 20a and 21a indicated diagrammatically for driving the rolls 20 and 21, respectively. The stock flow valve'17 may be controlled manually or at a control panel C via conventional control connections indicated diagrammatically at 17a. Although the instant invention may be employed in an open topped headbox wherein the stock fiow valve 17 would be the principal control for the rate ofrfiow of stock through the headbox, it is preferable to employ a headbox such as the headbox 11 having a closed top 26 and connected to a suitable source of gas under pressure such as air at A through a control valve indicated at 2'7 for controlling the pressure of gas in the headbox 11 against the top of the stock stream therein.

In order to maintain a stock level L-2 in the headbox 11, while using pressurized air, one simple expedient (dis-- closed -in the aforesaid Patent No. 2,664,033) involves the use of a pipe 2S providing a vent at the level L-2 to atmos- In operation, if the stock level drops below the vent 28, pressurized air is released to the atmosphere and the pressure against the stock in the headbox 11 decreases so that the stock level may rise again to the pipe 28; and when the stock level rises above the pipe 28, the pressure within the headbox 11 will increase, tending to drive the level of the stock stream back down to the vent 28. Other conventional level control expedients are known, which include the use of a level sensing device 29 for sensing the level L-2 and signalling the sensed level L-2 backto the control panel C, which in turn (using conventional control devices) may actuate the air pressure valve 27, the stock flow valve 17 and/or a conventional air vent mounted in a suitable aperture at 30 (or even at 28) in the headbox 11. Such various means for ycontrolling the gas pressure against the top of the stock stream in the headbox are per se Well known in the art.

The rectifier roll 21v is positioned at the tapered approach to the slice 22 between the front wall portion 12a and the fioor 13, but spaced from the slice opening 22 a distance A to afford dissipation of turbulence at the offrunning side of the roll 21 upstream of the slice opening 22. The roll 21 has a diameter 21D, and the distance A between the periphery of the roll 21 and the slice opening 22 is preferably about 1/2 to 2 times the roll diameter 21D, so that the turbulence generated in the stock stream by the rectifier roll 21 may be substantially dissipated before the stock stream reaches the `slice opening 22.V In this respect, it will be seen that the region 21C of higher turbulence at the off-running side of the rectifier roll 21 is generally triangular in cross section with an apex of the triangle aimed at the slice opening 22. Depending upon the rectilinear speed of stock flow in the headbox, the region 21C of higher turbulence at the off-running side of the rectifier roll 21 may extend from about 1/zto about 1 times the diameter 21D from the periphery of the roll 21 in the direction of the slice 22.

The rectifier 21 is preferably mounted for close ruiming relation not-only to the fioor 13 but also to the front wall 12a of the headbox 11, as well as the side walls 15 and 16. Actually, the roll 21 may be spaced as little as about 1A inch from the fioor 13, for minimum operating clearance; but as much as 1/2 to 11/2 inches from the front wall 12a to accommodate slice adjustment. Also, the rectifier roll 20 in the intermediate location in the' headbox 11 .is mounted for closev running relation to the headbox floor as well as the side walls 15V and 16. The rectifier roll 20 has a diameter 20D; and it will be seen that the rectifier roll 20 is spaced upstream from the rectifier roll 21 to afford dissipation of the turbulence 'at the off-running side of the rectifier roll 20 upstream of thefroll 21. As indicated, the triangularly shaped region 20C of maximum turbulence at the off-running side of the roll 20 extends beyond the periphery of the roll 211 about 50 to 100% of the diameter 20D, and the space B between the peripheries of the rolls 20'and 21 is preferably within the range of about 1 to 2 times 26D.

Referring specifically to FIGURE 2, it wifl be noted that the end mounting of the roll 20 on the side Wall 1d is shown in some detail, and it will be appreciated that the rectifier roll 21 is mounted similarly (except that it does not have internal baflies). As shown in FIGURE 2, the rectifier roll 20 presents to the stock stream a radially perforated cylindrical tube 31 extending between the side walls 15 and 16, and having a myriad of perforations extending the full length thereof, including partial perforations defining scalloped ends 31A for close running relation to the side walfs 15 and 1e (along the lines shown in US. Patent No. 2,5 66,449, issued September' 4, 1951). As indicated in some detail in the aforesaid Patent No. 2,699,096, in order to provide a minimum `restriction to stock flow through the rectifier roll 20 (or 21), coupled with maximum operating cleanliness and flow stabilization, itis advisable to provide the roll with a substantial area of perforations, in a generally uniform perforation pattern having holes of substantially the sameV size.

An open area of about 40% is preferred for lthe rolls 20 and 21. It will thus be seen that there are holes 32a. through 32x closely spaced together in one generally axially aligned row of holes and in the immediately ad jacent row of holes 33a-33x, the holes are also axially aligned and closely spaced together but positioned substantially intermediate the holes in the row 32a-32x. This is the pattern around the entire periphery of the roll 20 and it includes a circumferential column of partialV holes (indicated at 34) which form the scalloped end for the roll.

The roll 20 is also provided with a plurality of radial bafiies 35 36, 37, etc. extending across the interior of the tube 31 and axially spaced along the lengthV thereof to assist in channeling stock flow therethrough and to thereby minimize cross velocities and eddycurrents in the stock stream flowing through the tube 31. The roll 21 is provided with outermost bafiies c g. 35 but not interna] baflies 36, 3'7, etc. It will also be seen that the outermost baffle 35 is spaced axially inwardly from the i scalloped end 34 of the tube 3l so as to afford an unobstructed end 34 for the tube 3l for the flow of stock between the recessed baille and the side wall lo of the headbox. The outermost baie 35 is positioned inwardly at least suliiciently far to clear the scalloped openings 34, and preferably to be centered on an interior circumferential column of full holes. As shown in Fl- URE 2, the outermost head 35 is centered on the outermost circumferential column of full holes, which would include the holes designated 32a.

In connection with the mounting of the rectifier roll 2f? (and 2l) for rotation, it will be seen that at each end of the roll 2u there is provided a stub shaft 4@ secured to the outermost baffle 35 and extending through the side wall lo to be received by a pair of spaced bearings 41 and 42 for stabilizing the position of the rotating stub shaft, as described in U.S. Patent No. 3,026,- 934, issued March 27, 1962.

Referring more specifically to FlGURES 3 and 4, it will be seen that the mounting of the outermost baille or head 35 has a number of structural advantages over the prior art. t will be seen that the baffle 35 has a generally streamlined contour, tapering radially outwardly from an axial socket 35A having an axial dimension ofabout 11/2 inches for a l2 or 13 inch diameter roll (or an axial dimension of about l to 2 times the diameter of the perforations in the roll), which is tapered down to a relatively thin periphery at 35B of about 1A to of the diameter of the perforations. The thin outer periphery 35B of the bafiie 35 is actually spaced closely from the interior of the perforated tube 3l by about 1A to 3A times the diameter of the perforations in the tube 3l (and preferably about 5/8 inch), and the baffle is actually mounted within the tube 3l on a plurality of peripherally spaced pins 35C, 35C, etc. Each of these pins extends radially outwardly from the thin periphery 35B of the baille 35 and each of these pins 35C has a generally flattened end 35D which has approximately the axial dimension of the thin bafiie periphery 35B to which it is welded. The pins 35C at their radial outer extremity have a generally rounded or circular cross section 35E which is welded to the inner periphery to the tube 3l at appropriate land areas in between perforations (indicated in FIGURE 3 at P-l and P-Z). lt has been found that the foregoing streamlined contour of the baffle 35 and its associated mounting pins 35C creates a minimum undesirable obstruction to the flow of stock in the region of the ends of the perforated tube 3l and affords distinctly superior uniformity in the flow of the stock from wall to wall between the side walls l5 and le in the headbox il.

In the rectifier rolls of the preferred size used in the practice of the instant invention, the perforations may range in diameter from about a minimum practical size of 1/2 to 3A of an inch to a maximum practical size of about 1% to l/z inches, and preferably the perforations are about 1 inch in diameter. Also, the pins 35 are preferably about 1A to @A of the hole diameters in diametrical dimension at the end engaging the interior of the tube 3l, and these pins are peripherally spaced about the bafiie 35 substantially uniformly, with the average peripheral spacing ranging from about l5 to about 6G", with the preferred spacing of about 24 as indicated in FlGURE 3 hereof.

Also as indicated in FlGURE 4 of U.S. Patent No. 3,026,934, and FIGURE 4 hereof, the shaft 4@ is received in the head socket 35A, but the head socket 35A also n carries an annular member 46A preferably made of hardened rubber or other suitable resilient solid elastomer which is capable of resisting the radial load applied thereto by the weight of the rectifier roll 21 carried by the head 35, but such annular resilient member ifi-A is sufficiently resilient to prevent the shaft from imposing any moment or bending load on the head 35. A slightly dished cap SSG is welded to the central portion of the head 35 at the back of the socket 35A for the purpose of providing the desired smooth outer lines and streamlined contour of the head 35. The foregoing rectifier roll structure (although also used for the roll 18 with the internal baffle) has been found to be particularly suitable for use as the slice roll 2l, or the roll at the approach to the slice preferably without the internal baies 36, 37, etc., because of the improved flow characteristics in the resulting stock stream passing through the slice opening 22.

lt will also be noted that the headbox 11 is a baieless headbox in that it does not provide any interior baffles. ln fact, the sole restriction to the flow of the stock stream through the headbox 1l is afforded by the rectifier rolls 20 and 2l (between the fioor inlet l@ and the slice opening 22). It will be appreciated that the various walls and floor l2, 13, lli, 15 and i6 of the headbox lll restrict the flow of the stock stream in Athe sense that they restrict it to a predetermined desired direction, but this actually amounts to a definition of the stock stream per se; whereas the rectifier rolls 2Q and 2l are positioned in this stream and with the stream flowing therethrough, such rectifier rolls Ztl and 21 are the sole restriction to the of the stock in such stream through the headboX; and internal headbox baffles or other ow controlling or restricting devices are avoided (as indicated in Patent No. 2,664,033).

As previously mentioned, heretofore in attempts to operate one roll deep headboxes, a number of unexplained but undesirable results were obtained. In such cases a headbor: of the general construction of the headbox 11 was used with substantially identical rectifier rolls in the positions 2@ and 2l shown in FIGURE l. ln spite of the fact that the rectifier rolls used were designed to afford minimum restriction to the flow of stock therethrough (i.e., about 50% to 56% open area), such rectifier rolls did provide some restriction to the flow of stock therethrough and such restriction involves an energy drop across the rectifier roll with a corresponding increase in rectilinear velocity in the stock stream. It was thus found that if such a headbox were operated at levels substantially below the top portions of the two rectifier rolls, at levels substantially above the top portions of the two rectifier rolls, or even at levels just barely suiiicient to submerge the rear roll of the two (in the case of said substantially identical rectifier rolls) the net result was an undesirable stock flow through the slice 22 as manifested in the forming operation. lt is now believed that certain of these difficulties were caused by the fact that the stock passing through the rectifier roll in the position 20 was actually undergoing a substantial reduction in energy and a velocity change, whereas any stock flowing over the top of the rectifier roll 2@ was not undergoing the same velocity change or the same rectification so that control of thevelocity profile was being lost. lf, in contrast, the headbox were operated so that the level L-l at the immediate upstrearn side of the rectifier roll in the position 2@ were just barely sufficient to submerge this roll (ie. less than about 1/z of the perforation diameters), then an undesirable flow of stock at the slice 22 is also obtained using a substantially identical rectifier roll in the position 2l; and this was believed to be the result of a flow problem which is shown essentially diagrammatically in FIGURE 5.

ln FIGURE 5, it will be seen that elements corresponding to substantially identical elements in FIGURE l are shown using primed reference numerals. It will be seen that the level )lj-2 at the immediate upstream side of the rectifier roll 2l' is substantially below the top of the rectifier roll 2l', and as the roll 2l rotates clockwise, the top portion of the roll 2l leaves the stock stream at approximately an angle 61 to level L-Z, which is a sufficiently large angle to result in each hole functioning as a weir with a waterfall of stock indicated at S-l and S-Z from the perforations P-S and P4 into the pool of stock at a lower level LL?) within the roll 2l. The lower level L-3 is occasioned by the flow restriction in the stock yand this is particularly .true at higher gallonages.

passing through the perforations. This results in undesirable creation of flocks in the stock as well as the entrapment of air in the body of the stock. In addition, as the rectifier roll 21 enters back into the stock stream L3 at approximately an angle of 02, additional air is pumped into the stock stream, as indicated by the air bubbles at A-1 at the immediate downstream side of the rectifier roll 21. The rapidly flowing stream of stock then passes on through the slice 22 with flocks and air bubbles entrapped therein so as to produce undesirable paper formation. Comparable undesirable results are obtained, if the roll 21 is rotated counterclockwise.

In the past rectifier rolls have been used with all types of hole sizes, patterns, wall thicknesses and covers in an attempt to eliminate strings and lumps. The most important factor in maintaining a rectifier roll in clean condition has been found to be the land area or width between the holes. A narrow land area between the holes will create strings and lumps, while Wider land areas will not. Increased land areas will decrease the percentage of open area in the rectifier rolls. .As previously indicated, rectifier rolls in the past have been employed having 50% to 56% open areas, with such rolls being used in the slice and headvat position. It has now been'found and established experimentally that rolls with approximately 40% open area (i.e. 35% to 45%) and a 5/16 inch wall thickness without additional covering appear to give' the best performance with respect to the elimination of lump formation. With 40% open area, however, there is increased energy drop through the rolls and this tends to create even greater difficulties with respect to the control of the level in the headboxes of the type under consideration. In particular, this increased drop through `the-rectifier rolls has. increased the problem of running the correct pond level at the slice rectifier roll position (ie. the position of the roll 21). The reduced open area has also been found to be beneficial, however, with respect to superior stabilization iiow and this makes possible the operation of the slice rectifier roll 21 without internal baffles or fins.

It has now been found that With the stock level L-2 maintained just slightly above the slice roll 21, disturbances of the type described in connection with FIGURE 5 hereof are substantially eliminated. Preferably, the level` L-2 is maintained slightly over the top of the rectifier roll 21 as it rotates in either direction, clockwise or counterclockwise. It has alsoy been found that, if the rectifier roll 2t) has substantially the same diameter as the rectifier roll 21, and the level L-Z is maintained just barely sufficient to submerge the slice roll 21, then there is a fiow of stock over the top of the headvat roll 2t), which effectively bypasses the headvat roll 20. Any disturbance crea-ted in the back of the headbox is thus'carried over the top of the headvat roll Ztl to the slice; By using a larger roll 2t) in the headvat position, the level at the slice roll 21 can always be held just over the top without bypassing over the top of the headvat roll 2f?.

Depending upon the gallonage and drop through the rolls and .21, the level lf2 at'the slice roll 21 isfheld and the level L-1 at the headvat roll Ztl will vary. The combination of the smaller roll 2.1 at the slice land the larger roll 20 at the headvat position permits operation at higher gallonage in a given headbox while still-maintaining control of the tiow.

It will thus be seen that in FIGURE 1, the level L-2 is maintained just barely sufficient .to submerge the slice rectifier roll 21; and the intermediate or headvat rectifier roll 2t) upstream from the slice roll 21 has a diameter that is larger than the diameter of the slice roll ,21. The floor 13 is substantially horizontal and there must be a corresponding difference in the diameters of the rectifier rolls Ztl and 21 so that the larger rectifier roll 20 with its corresponding restrictive effect upon the iiow of stock in the headbox 11 may cooperate with the stock flow means 17 (and preferably also with the means 27 for controlling the gas pressure on the top surface of the stock stream) so as to maintain a level of stock L-2 downstream of the headvat roll 26 and atthe immediate upstream side of the slice roll 21 that is barely suficient to submerge the slice roll 21. It will be appreciated that at a given gas pressure on the surface of the stock stream, the level L-2 .at the immediate upstream side of the roll 21 is controlled by the combination of the stock stream control valve 17 and the restrictive effect of the rectifier roll 21 on the flow of stock. If the gas pressure on the level4 L-2 is controllable as. in the closed headbox 11, then this variable also cooperates with the elements 17 and 2u to control the downstream level L-Z. In addition, it will be appreciated that at least to some extent the rateof rotation (asby the motor 29a) of the headvat roll 20 would be part of the'overall restrictive effect of the rectifier roll and the restrictive effect of the rectifier roll 2t) is additionally affected and thereby controlled by changes in design of the perforation pattern, the perforation sizes,` theactual thickness (ie. radial dimension of the shell) of the perforated tube. The corresponding structural features of the slice roll 21 also determine zand/or control its restrictive effect upon the stock stream and thus contribute to the control of the level L-Z immediately upstream thereof. Also, the means 25 for varying the slice opening 22 will have a definite effect upon the various levels of stock in the headbox 11.

As previously indicated, it is generally desirable to operate the headbox 11 so that the level L-2 is just barely sufficient to submerge the slice roll 21. Under spceial conditions, however, it is possible to run using low gallonage and 10W stock velocity at a level at approximately the center line of the rectifier rolls to increase velocities in the box and add more activity on the Fourdrinier table. Under this condition any disturbance discharging from the slice roll has increased length and time to level out before reaching the slice 22 (since the distance from the rectifier roll periphery 21 to the Slice 22 increases as the stockv level L-2 drops).

Referring briefly to FIGURES 6 and 7, it will be seen that somewhat different headbox designs are Vshown therein, but in FIGURE 6, elements that are substantially the samein general structure and function as those shown in FIGURE 1 are designated by the same reference numeral in the 100 series and in FIGURE 7 elements that are substantially the same in structure and function as those shown in FIGURES 1 and 6 are designated by the same reference numeral in the 2G() series. It will be appreciated that the headboXes 111 and 211 are equipped with the various stock ow means (17, etc'.), gas pressure control means (27, 28, 29, 3d C and A, etc.) as are shown in FIGURE l.

In FIGURE 6, the essential functional difference is that the door 113 for the headbox 111 is slanted upwardly; and in order to maintain the desired different levels L-1t1 at the upstream side of the rectifier' 120 and L-llfl2 at the upstream side ofthe rectifier roll 121, it is necessary in this arrangement to use a substantially smaller rectifier roll 121. Y

In FIGURE 7, however, it will be notedthat the floor 213 of the headbox V211 is slanted downwardly from the horizontal toward the slice 122; and in this arrangement the upstream level lis-291 for the upstream rectifier yroll 220 may be maintained so as tobarely submerge the rectifier roll 22@ While the lower downstream level L-202; is maintained so as to just barely submerge the slice roll 221. Because of the downward incline of the arssfiss 9 substantially identical and therefore rectifier rolls 220 and 211.

The difference betwen the levels L-Zl (L-il and L-Zill) and L-Z (L-lilZ and L-ZZ) for conventional high speed stock flow of 60 to 1GO gpm. per inch of width may range from about 0 to 3 inches, or expressed in other terms, may range from about 0 to 3 times the perforation diameters PD (FIGURE 3). The shell thickness ST (FlGURE 3) may also range from about 1A to inch (preferably about 5%6 inch), or about 1A to times the preferred perforation diameter PD.

It will be understood that modifications and variations may be effected Without departing from the spirit and scope of the novelconcepts of the present invention.

We claim as our invention:

l. A rectifier roll adapted to be rotatably mounted for close running relation to paper machine headbox side walls, said rectifier roll comprising a radially perforated cylindrical tube with scalloped ends, a plurality of radial bafiies extending across the interior of the tube and axially spaced along the length of the tube, each of the outermost baffles in the tube having a streamlined contour tapering radially outwardly from an axial stub shaft rereceiving socket to a thin periphery closely spaced from the interior of the tube but secured to the tube axially inwardly from the scalloped ends by peripherally spaced pins extending radially outwardly from such thin periphery, a stub shaft at each end of the tube adapted to extend inwardly through the headbox side walls and received in the socket of each of the outermost baffles, and annular resilient means in each socket interposed between the shaft and the outermost baille at each end of the tube to accommodate relative tilting movement between the shaft and the baiiie carried thereby during rotation of the rectifier roll.

2. A rectifier roll adapted to be rotatably mounted for close running relation to paper machine headbox side walls, said rectifier roll comprising a radially perforated cylindrical tube with scalloped ends, a plurality of radial batlies extending across the interior of the tube and axially spaced along the length of the tube, each of the outermost baflies in the tube having a streamlined contour tapering radially outwardly from an axial stub shaft receiving socket to a thin periphery closely spaced from the interior of the tube, a plurality of peripherally spaced generally cylindrical pins secured to the interior of the tube axially inwardly from each scalloped end thereof and having flattened ends of substantially the thickness of and secured to the thin outermost batile periphery to mount such baffle in the tube, and annular resilient means in each socket adapted to be interposed between a stub shaft and the outermost baille at each end of the tube to accommodate relative tilting movement between the shaft and the baiiie carried thereby during rotation of the rectifier roll.

3. A rectifier roll adapted to be rotatably mounted for close running relation to paper machine headbox side walls, said rectifier roll comprising a radially perforated cylindrical tube with scalloped ends, a pair of radial heads extending across the interior of the tube, each of the heads in the tube having a streamlined contour tapering radially outwardly from an axial stub shaft receiving socket to a thin periphery closely spaced from the interior of the tube, a plurality of peripherally spaced generally interchangeable cylindrical pins secured to the interior of the tube axially inwardly from each scalloped end thereof and having flattened ends of substantially the thickness of and secured to the thin outermost head periphery to mount such head 5 in the tube, and annular resilient means in each socket adapted :to be interposed between a stub shaft and the head at each end ofthe tube to accommodate relative tilting movement between the shaft and the head carried thereby during rotation of the rectifier roll.

4. In a headbox having side walls, a licor and a front wall defining with the floor a tapered approachto a slice opening, iirst means for liowing a stream of stock through the headbox and out the slice, second means in control of gas pressure against the top of such stock stream, a first rectifier roll at the tapered approach but spaced from the slice opening to afford dissipation of turbulence at the olf-running side of the first roll upstream of the slice opening, and a second rectifier roll in the headbox spaced upstream from the first roll to afford dissipation of the turbulence at the olf-running side of the second roll upstream of the first roll, each of said rectifier rolls presenting a radially perforate cylindrical tube having perforations within the diameter range of 1/2 to 11/2 inches and presenting a substantially uniform 'pattern in the cylindrical tube walls which have a thickness of substantially 1A to 3/s times the perforation diameters, each said tube extending between the side walls and having stub shaft journalling the tube for rotation and resiliently mounting the tube ends on thin heads of streamlined contour tapering radially outwardly from said shafts mounting peripherally spaced pins to connect to the inner periphery of each such perforate tube closely spaced from the extremities of the tube inwardly and in close running relation to the headbox side walls, said shafts positioned r in the side walls to mount said tubes in close running relation to the headbox floor whereby the rotary perforate tube presents a substantially uniform restriction between the side walls to the flow of stock in the stream in the headbox, said second reotier roll being larger in diameter than the first roll and cooperating with said first means and second means to maintain a first level of stock downstream of the second roll that is barely sufficient to submerge the first roll by less than substantially 1/2 of its perforation diameters and a second stock level upstream from the second roll that is vbarely suiiicient to submerge the second roll by less than substantially 1/2 of its perforation diameters, with the difference between said second stock level and said first stock level being 50 substantially in the order of three times the aforesaid perforation diameters for high speed stock flow in the order of 60 to 100 gallons per minute per inch of headbox width.

References Cited in the file of this patent OTHER REFERENCES Van der Meer, Hydraulics of Flowbox and Slice, Tappi, vol. 37 No. 11, November 1954, pp. 502-511. 

1. A RECTIFIER ROLL ADAPTED TO BE ROTATABLY MOUNTED FOR CLOSE RUNNING RELATION TO PAPER MACHINE HEADBOX SIDE WALLS, SAID RECTIFIER ROLL COMPRISING A RADIALLY PERFORATED CYLINDRICAL TUBE WITH SCALLOPED ENDS, A PLURALITY OF RADIAL BAFFLES EXTENDING ACROSS THE INTERIOR OF THE TUBE AND AXIALLY SPACED ALONG THE LENGTH OF THE TUBE, EACH OF THE OUTERMOST BAFFLES IN THE TUBE HAVING A STREAMLINED CONTOUR TAPERING RADIALLY OUTWARDLY FROM AN AXIAL STUB SHAFT RERECEIVING SOCKET TO A THIN PERIPHERY CLOSELY SPACED FROM THE INTERIOR OF THE TUBE BUT SECURED TO THE TUBE AXIALLY INWARDLY FROM THE SCALLOPED ENDS BY PERIPHERALLY SPACED PINS EXTENDING RADIALLY OUTWARDLY FROM SUCH THIN PERIPHERY, A STUB SHAFT AT EACH END OF THE TUBE ADAPTED TO EXTEND INWARDLY THROUGH THE HEADBOX SIDE WALLS AND RECEIVED IN THE SOCKET OF EACH OF THE OUTERMOST BAFFLES, AND ANNULAR RESILIENT MEANS IN EACH SOCKET INTERPOSED BETWEEN THE SHAFT AND THE OUTERMOST BAFFLE AT EACH END OF THE TUBE TO ACCOMMODATE RELATIVE TILTING MOVEMENT BETWEEN THE SHAFT AND THE BAFFLE CARRIED THEREBY DURING ROTATION OF THE RECTIFIER ROLL.
 4. IN A HEADBOX HAVING SIDE WALLS, A FLOOR AND A FRONT WALL DEFINING WITH THE FLOOR A TAPERED APPROACH TO A SLICE OPENING, FIRST MEANS FOR FLOWING A STREAM OF STOCK THROUGH THE HEADBOX AND OUT THE SLICE, SECOND MEANS IN CONTROL OF GAS PRESSURE AGAINST THE TOP OF SUCH STOCK STREAM, A FIRST RECTIFIER ROLL AT THE TAPERED APPROACH BUT SPACED FROM THE SLICE OPENING TO AFFORD DISSIPATION OF TURBULENCE AT THE OFF-RUNNING SIDE OF THE FIRST ROLL UPSTREAM OF THE SLICE OPENING, AND A SECOND RECTIFIER ROLL IN THE HEADBOX SPACED UPSTREAM FROM THE FIRST ROLL TO AFFORD DISSIPATION OF THE TURBULENCE AT THE OFF-RUNNING SIDE OF THE SECOND ROLL UPSTREAM OF THE FIRST ROLL, EACH OF SAID RECTIFIER ROLLS PRESENTING A RADIALLY PERFORATE CYLINDRICAL TUBE HAVING PERFORATIONS WITHIN THE DIAMETER RANGE OF 1/2 TO 1 1/2 INCHES AND PRESENTING A SUBSTANTIALLY UNIFORM PATTERN IN THE CYLINCRICAL TUBE WALLS WHICH HAVE A THICKNESS OF SUBSTANTIALLY 1/4 TO 3/8 TIMES THE PERFORATION DIAMETERS, EACH SAID TUBE EXTENDING BETWEEN THE SIDE WALLS AND HAVING STUB SHAFT JOURNALLING THE TUBE FOR ROTATION AND RESILIENTLY MOUNTING THE TUBE ENDS ON THIN HEADS OF STREAMLINED CONTOUR TAPERING RADIALLY OUTWARDLY FROM SAID SHAFTS MOUNTING PERIPHERALLY SPACED PINS TO CONNECT TO THE INNER PERIPHERY OF EACH SUCH PERFORATE TUBE CLOSELY SPACED FROM THE EXTREMITIES OF THE TUBE INWARDLY AND IN CLOSE RUNNING RELATION TO THE HEADBOX SIDE WALLS, SAID SHAFTS POSITIONED IN THE SIDE WALLS TO MOUNT SAID TUBES IN CLOSE RUNNING RELATION TO THE HEADBOX FLOOR WHEREBY THE ROTARY PERFORATE TUBE PRESENTS A SUBSTANTIALLY UNIFORM RESTRICTION BETWEEN THE SIDE WALLS TO THE FLOW OF STOCK IN THE STREAM IN THE HEADBOX, SAID SECOND RECTIFIER ROLL BEING LARGER IN DIAMETER THAN THE FIRST ROLL AND COOPERATING WITH SAID FIRST MEANS AND SECOND MEANS TO MAINTAIN A FIRST LEVEL OF STOCK DOWNSTREAM OF THE SECOND ROLL THAT IS BARELY SUFFICIENT TO SUBMERGE THE FIRST ROLL BY LESS THAN SUBSTANTIALLY 1/2 OF ITS PERFORATION DIAMETERS AND A SECOND STOCK LEVEL UPSTREAM FROM THE SECOND ROLL THAT IS BARELY SUFFICIENT TO SUBMERGE THE SECOND ROLL BY LESS THAN SUBSTANTIALLY 1/2 OF ITS PERFORATION DIAMETERS, WITH THE DIFFERENCE BETWEEN SAID SECOND STOCK LEVEL AND SAID FIRST STOCK LEVEL BEING SUBSTANTIALLY IN THE ORDER OF THREE TIMES THE AFORESAID PERFORATION DIAMETERS FOR HIGH SPEED STOCK FLOW IN THE ORDER OF 60 TO 100 GALLONS PER MINUTE PER INCH OF HEADBOX WIDTH. 